NSTS Bancorp, Inc. Quarterly report pursuant to Section 13 or 15(d)

Loans and allowance for loan losses - Loan balances based on risk rating (Details)

Loans and allowance for loan losses - Loan balances based on risk rating (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 96,182	$ 98,659
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total	95,668	97,863
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total	409	516
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total	105	280
First mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	95,858	98,274
First mortgage loans \| 1-4 family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total	87,184	87,197
First mortgage loans \| 1-4 family residential \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total	86,670	86,500
First mortgage loans \| 1-4 family residential \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total	409	417
First mortgage loans \| 1-4 family residential \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total	105	280
First mortgage loans \| Multi-family
Financing Receivable, Credit Quality Indicator [Line Items]
Total	4,221	5,737
First mortgage loans \| Multi-family \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total	4,221	5,737
First mortgage loans \| Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total	4,453	5,340
First mortgage loans \| Commercial \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total	4,453	5,340
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	324	385
Consumer loans \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 324	286
Consumer loans \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total		$ 99